1. Field of the Invention
The present invention relates to a polyhydric phenol compound and a positive resist composition which comprises the same and has high sensitivity and a large depth of focus.
2. Description of the Related Art
A composition containing a compound having a quinone diazide group and an alkali-soluble resin finds use as a positive resist, because upon exposure to light having a wavelength of 300 to 500 nm, the quinone diazide group decomposes to form a carboxyl group whereby the originally alkali-insoluble composition becomes alkali-soluble. The positive resist composition has much better resolution than a negative resist composition and is used in the production of integrated circuits such as IC or LSI.
Recently, particularly with integrated circuits, miniaturization has proceeded with a rise in the integration level, which results in demands for formation of patterns of submicron order. To satisfy such demands, a step-and-repeat type reduction projection exposure apparatus, namely a stepper is used as an exposure apparatus.
When a numerical aperture (NA) of a reduction projection lens of the stepper is increased, a resolution is increased but a depth of focus is decreased. Because of the step-and-repeat type, a throughput of the stepper is smaller than that with a batch exposure system. Therefore, the resist composition is required to have a much larger depth of focus and better sensitivity.
However, a resist composition comprising a conventional quinone diazide compound and a conventional alkali-soluble resin has a limit in improvement of the depth of focus and the sensitivity.
For example, if an amount of the quinone diazide compound is increased to increase the depth of focus, serious problems such as deterioration of sensitivity and increase of residues after developing arise.